It's making a little more sense now.
They shipped Ground Advantage.
You really need to have the weights right or you'll get a postage due.
The pseudocode for that is something like
If postage due.
Then Attempt debit account on record for additional postage
If no account on record and postage is due.
Then return to sender
If sender return address is invalid..
and that's where I'm not sure... I know they'll just boomerang the package back if they can't autocharge your account for the overage.
And then if the return address is bunk I'm not sure what happens.
The tier system for weighed postage is not friendly. They would have done better to use flat rate boxes.
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